ML17266A084

LER 79-021/01T-0 on 790625:General Motors Notified Util That Turbocharger Thrust Bearing Could Be Damaged by Hot Starts W/Lube Oil Over 160 F.Vendor Recommends Eliminating Nonemergency Hot Starts While New Design Is Developed

ML17266A084
Person / Time
Site:	Saint Lucie
Issue date:	07/09/1979
From:	Shoppman M FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML17206A902	List: ML17206A901 ML17266A084
References
LER-79-021-01T-01, LER-79-21-1T-1, NUDOCS 7907180328
Download: ML17266A084 (3)

Text

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SV BNT OBSCRIPTTON AiIO PROBABI B CONSBCUBiICBB QIO During. an inves'ti ation resul tin from revio die 1-ures (LER 335-77-42), the. Electro Motive Division of General Motors re-ported that the turbocharger thrust bearing was-susceptible to dama e un-

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der repeated hot start conditions while the lube oil is above 160 degrees F. This is not a report that damage has occurred, nor has emergency start capability been impaired, therefore, there has, been no adverse affect on the safety of the plant. 30 T 3 9 CQVP. v04LYS LJ>>

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CAUSB OBSCRIPTION ANO CORABC'<<'IVB ACTIONS Q22 The potentia'1 for dama e'to the DG turbochar er thrust bearin is e-tablished because the circulating oil pump cannot produce the 30 PSI re-

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ty of the oil above 160 degrees F. Electro thtive has recommended interim action to eliminate non-emergency hot starts and is working on a new desig .

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, - REPORTABLE OCCURRENCE 335-79-21 LICENSEE EVENT REPORT

.PAGE ll(0 ADDITIONAL CAUSE DESCRIPTION AND CORRECTIVE ACTION The Electro Motive Division of General Motors has reported via Stewart and Stevenson Services and the Florida Power 8 Light Company Power Plant Engineering Department that their investigations into previous DG turbocharger failures have shown that the turbocharger thrust bearing is susceptible to damage under certain repeat hot start conditions which could ultimately result in turbo-charger failure. This condition is encountered only when restarting the engines between 15 minutes and 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> after a hot shutdown while the lube oil temperature is above 160 F. Due to the lower viscosity of the oil above 160 F, the circulating oil pumps cannot produce the 30 PSI required to maintain flow to the oil filter and cooler system and the system drains to the enoine sump. The oil normally in this system provides a "prime" for the main oil pump and without this "prime" the main'pumps cannot establish full oil pressure to the turbocharger thrust bearing before operating speed is reached and ensuing damage could occur; If the engines are started within 15 minutes, the oil has not had time to drain and the situation does not exist. The damage occurs as cumulative wear on the bearings,not as an immediate failure.

'Therefore, an "emergency" start from a hot shutdown would not be prevented.

Electro Motive has recommended the following corrective actions whi ch will be incorporated into the plant maintenance, test, and operations procedures.

(1) After hot shutdown, ei ther restart wi thin 15 minutes or allow the engine 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> to cool after it has been operated before restarting. This is not'applicable to emergency starts.

(2) Ensure circulating oil pump operation for a minimum of 30 minutes after changing oil filters or draining the accessory oil system. Idle start the engine if poss-ible to ensure accessories are completely filled before rapid starting.

(3) Identify and correct all leaks at the top of the oil coolers to avoid rapid draining of the cooler.

In,~addition to the above, Electro Motive is currently working on the develop-ment of a modification package, which is to be available in about 6 months.

It should be noted that, although we are reporting this development as a prompt reportable occurrence, it is the result of investigation of a previous occurrence and is being reported to supplement the previous report (335-77-42).